JPH03103366A - Castable refractory for molten iron pretreating lance - Google Patents

Abstract

PURPOSE:To improve oxidation, melting loss, thermal shock resistance, etc., by using a specific amount of needlelike petroleum coke subjected to hydrophilization treatment as a carbonaceous material for a castable refractory used in Al2O3-SiC-C-based lances for pretreating molten iron. CONSTITUTION:(A) Alumina is mixed with (B) silicon carbide, (C) 3-15wt.% needlelike petroleum coke subjected to hydrophilization treatment and (D) a required aggregate (e.g. fine silica powder), a binder (e.g. alumina cement), etc., to produce a castable refractory used in pretreating lances for molten iron. Furthermore, the needlelike petroleum coke must be heat-treated at a high temperature of about >=1300 deg.C and have about >=95% fixed carbon content. The hydrophilization treatment of the needlelike cake is carried out by coating the surface thereof with a very small amount of a surfactant (e.g. an alkylbenzenesulfonic acid-based surfactant).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the material of the refractory sheath of a lance pipe used in preliminary treatments such as desiliconization, desulfurization, and dephosphorization of hot metal.

[Prior art]

Lance vipes for pre-treatment of hot metal are used to inject treatment agents during the desiliconization, desulfurization, and dephosphorization treatments of molten metal, and are used to inject treatment agents into the molten metal. used under conditions.

Currently, lance pipes are made of stainless steel, which is made by adding a binder such as clay or aluminium cement to aggregate of one or more types of refractory raw materials such as alumina, silica, and magnesia around a metal core pipe. It is used in constructions coated with monolithic refractories containing fibers. Cracks and peeling occur due to melting damage and thermal shock in the slag line portion or near the discharge hole of these jacketed refractories, which greatly affects the durability of the lance pipe.

[Problem to be solved by the invention]

In general, in alumina-silica refractories, the higher the aluminium content, the better the erosion resistance, but on the other hand, the coefficient of thermal expansion of the refractory increases, the penetration of slag increases, and the thermal shock resistance deteriorates. . Under these circumstances, in recent years, SiC and carbon have been used to improve thermal shock resistance and suppress slag penetration.

However, in the case of caster pull refractories, if a large amount of carbon raw material is added, a large amount of kneading water is required to obtain the appropriate viscosity, and mechanical strength decreases, so it is not possible to use a large amount of carbon raw material. . Therefore, carbon raw materials that are relatively easily wetted by water, such as tar pitch, have been used, but Yuichi Lupisochi contains volatile matter, which causes problems such as the construction material becomes a bolus after heating and is easily oxidized.

This invention was proposed in view of the above-mentioned conventional circumstances, and has high oxidation resistance, less cracking and peeling damage, and
The purpose of the present invention is to provide a castable refractory for hot metal pretreatment lances that has excellent erosion resistance.

[Means to solve the problem]

In order to achieve the above object, the present invention provides Al zO
x Si C We would like to provide a castable refractory for hot metal pretreatment lance using 3 to 15% by weight of needle petroleum coke subjected to parent wood treatment as a carbonaceous raw material for castable refractory for hot metal pretreatment lance of C type. That is.

[Function] The needle petroleum coke mentioned above must be heat-treated at a temperature of 1,300°C or higher and have a fixed carbon content of 95% or more, and those with a fixed carbon content of less than 95% will not volatilize. The oxidation resistance of the refractory deteriorates due to the combustion.

In addition, the particle size of the needle petroleum coke is preferably 0.5 mm or less; if it exceeds 0.5 mm, the needle petroleum coke itself is a bolus, which reduces the density of the castable refractory, resulting in good oxidation resistance. I can't get sex.

The amount of needle petroleum coke used is preferably 3 to 15% by weight. If it is less than 3% by weight, it will not be possible to suppress the penetration of slag and the erosion resistance will decrease, and if it exceeds 15% by weight, the castable Density decreases, resulting in poor oxidation resistance and erosion resistance.

The factors contributing to the improvement in oxidation resistance of the castable refractory for lances in the present invention are as follows.

In other words, needle petroleum coke has a high fixed carbon content, is extremely anisotropic, and has an oxidation initiation temperature of approximately 700°C, which is higher than that of tar pitch. . Furthermore, by treating the needle petroleum coke with parent wood, it becomes well wetted with water and a dense workpiece can be obtained even when the amount of water used for kneading in the caster pull is small, and the workpiece becomes porous like when using a tar pinch. It's also because it will never happen again.

Furthermore, due to its shape, needle petroleum coke produces a drawing effect similar to that of the stainless steel fibers commonly used in caster pull, increasing the tensile strength and thermal shock resistance of the refractory material.

Furthermore, since the fixed carbon content is as high as 95%, it goes without saying that it is extremely resistant to wetting with slag and has improved resistance to erosion.

The parent wood treatment of needle petroleum coke is carried out by coating the surface with a very small amount of a surfactant, such as an alkylbenzenesulfonic acid surfactant.

The caster pull refractory of the present invention uses alumina and silicon carbide as main raw materials, and needle petroleum coke is added.
As other refractory raw materials, any known materials commonly used for caster pull refractories can be used. Further, in order to ensure the fluidity of the castapul refractory, alumina cement or the like can be added as a binder to increase the viscosity, alumina fine powder, silica fine powder, etc.

〔Example〕

The present invention will be explained below with reference to Examples and Comparative Examples.
The present invention is not limited to these examples.

The blending ratios of the castable refractories of Examples 1 to 3 and Comparative Examples are as shown in Table 1, and the respective castable refractories were cast.

The results of physical properties after firing, hot bending strength, slag test (erosion resistance), and oxidation resistance are shown in Table 2 below.

From the results shown in Table 2, it is clear that the castable refractories according to the present invention have extremely poor heat resistance, erosion resistance, and oxidation resistance.

In addition, in the slag test, the difference in the thickness of the sample before and after the test is taken as the amount of melting loss (related), and the melting loss tMff of Example 1 is
It is expressed as a solubility ratio when l is 100.

In addition, in the oxidation test, the thickness of the decarburized layer after the test was expressed as a ratio when Example 1 was taken as 100.

Next, a lance pipe for desiliconization injection was manufactured using the caster pull refractories obtained in Example 1 and Comparative Example 1, and as a result of using it in an actual machine, it was found that the lifespan of Comparative Example 1 was 5 charges. In comparison, the material of Example 1 had almost no cracks or peeling, and had little erosion damage to the treatment agent and slag after treatment, and could last for more than 10 charges.

Table ■: [l Lower margin Table 2 [Effects of the present invention] The castable refractory used for the outer refractory of the hot metal pretreatment lance pipe according to the present invention has excellent oxidation resistance, and is furthermore ANzOx SiC C-based refractory. It is possible to obtain an excellent refractory that also has melt resistance T4 properties and thermal shock resistance, which are the characteristics of products. Therefore, the durability of the hot metal pretreatment lance pipe can be improved.

Claims (1)

[Claims] (1) A castable refractory for a hot metal pretreatment lance using 3 to 15% by weight of needle petroleum coke subjected to hydrophilic treatment as a carbonaceous raw material for an Al_2O_3-SiC-C based castable refractory for a hot metal pretreatment lance.